Two Phase I Trials Launched

The Indian Council of Medical Research and IAVI have launched a Phase I trial to test the safety and immune responses elicited by two AIDS vaccine candidates administered sequentially in a prime-boost regimen. The trial known as P001 will enroll 32 volunteers at clinical trial centers in Pune and Chennai to evaluate different doses and vaccination regimens of the vaccine candidates. One candidate, TBC-M4, utilizes a modified vaccinia Ankara virus vector to deliver non-infectious HIV fragments in the hope of inducing an immune response against HIV. The candidate was developed in collaboration with the National Institute of Cholera and Enteric Diseases in India and was tested previously in a Phase I trial conducted in Chennai. In this trial, administration of TBC-M4 will be preceded by a prime vaccination with ADVAX, a DNA-based vaccine candidate, which was developed at the Aaron Diamond AIDS Research Center in New York City in collaboration with Rockefeller University and IAVI. Neither of the candidates being tested in this trial can cause HIV infection.

IAVI is also planning to begin enrolling volunteers in a Phase I trial of its adenovirus serotype 35 (Ad35)-based vaccine candidate. The trial will enroll 42 volunteers at the University of Rochester Medical Center who will be randomly selected to receive either two intramuscular injections of the Ad35-based vaccine candidate or placebo at three different doses. Clinicians will first administer the lowest dose and will review the safety data before proceeding to the next higher dose.

Ad35 is a serotype or strain of the common cold virus that researchers are using as a vaccine vector in this candidate to shuttle non-harmful fragments of clade A HIV, which is the predominant strain circulating in East Africa. The prevalence of naturally circulating Ad35 is much lower worldwide than the prevalence of adenovirus serotype 5, which was the virus used as a vector in Merck's AIDS vaccine candidate that was tested in the STEP trial. By using Ad35, it may be possible to circumvent issues involving pre-existing immunity to the viral vector (see VAX February 2005 Primer on Understanding Pre-existing Immunity). —By Regina McEnery